Not exactly. ACA imposes minimum Medical Loss Ratios. If they deny everything, the MLR would be zero and they would have to refund premiums.
The more care that's allowed, the more dollars they can keep. It's a complex optimization though; people like to pay less premiums, so an insurance company wants to price coverage low enough to attract customers and then allow enough care to keep the premiums without allowing so much as to reduce their margin.
The more care that's allowed, the more dollars they can keep. It's a complex optimization though; people like to pay less premiums, so an insurance company wants to price coverage low enough to attract customers and then allow enough care to keep the premiums without allowing so much as to reduce their margin.